Rheostat for controlling electrically-operated dental apparatus



(No Model.) 2 Sheets-Sheet 1.

J. P. B. FISKE. RHEosTAT P0P. GONTROLLING ELEGTRIGALLY OPBRATED DENTAL APPARATUS.

No. 508,692. Patented Nov. 14, 1893.

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, l 2 Sheets-Sheet 2. J. P. B'. FISKE.' RHEOSTAT FOR UONTROLLING ELEGTRIGALLY OPER-ATER vDENTAL APPARATUS.

(No-Model.)

No. 508,692. PatentedNov. 14, 1893;

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i' v I nnnnnnnnnnnnnnnnnnnnnnnnn ruin k\ i I WASHINGTON. UA C4 y Y v Dritten 'TATES flafrENtr .raient JONATHAN P. B. FISKE, OF LYNN,`ASSIGNOR lTO THE GENERAL ELECTRIC COMPANY, OF BOSTON, *MASSACHUSETTS y RHEOSTAT FOR CONTROLLINGELECTRICALLY-OPERATED DENTAL APPARATUS.

SPECIFICATION forming part of Letters Patent N o. 508,692, dated November 14, 1893. Application iiled July l0, 1893. `Serial No. 479,992- (No model.)

To all whom t may concern.' connection to the brush H, as seen in Figs. 2 Beit known that I, JONATHAN P. B. FIsKE,a and 3. The blocks F, F are hollowed out on citizen of the United States, residing at Lynn, their inside to atlord a seat for the spring G in the county of Essex and State of Massachuacting to force the brush H into contact with 5 setts, have invented certain new and usefulY the rows of rheostat contacts D, D. After 55 Improvements in Rheostats for Controlling the blocks F are placed in position they are Electrically-Operated Dental Apparatus, of secured to the brush holder by screws pass- Which the following is a specification. ing through holes drilled in each of the boxes. My invention relates to rheostats for con-I The construction thus described renders it iotrolling electrically operated dental apparaeasy to replace the brush or spring should 6o tus, and has for its object to provide a coneither one become damaged or worn.

troller of efficiency and simplicity in construe- Referring to Fig. 4, m, m, are the mains suption and operation and one capable ot' being plying current to the field magnet terminals used continuously withoutfatiguetothe oper- M, M. K, K are the coils of the motor field 15 ator. magnet and L is the armature supplied by 6 My invention is illustrated in the accomthe current from the terminals M, M. H, H, panying drawings, hereby referred to and show the brushes which are connected by flexiinade part of this specification, in which*v ble cables I, I, with the armature terminals. Figure 1 is a side elevation partly in sec- The course of the current is as follows: Enzo tion. Fig. 2 is a plan with one-half the top tering by the main m to the tield magnet ter- 7o broken away and showing the brush-holder minal M, it passes to the contact platesa, d in section, and Fig. 3 isa side elevation partly which are connected by a copper wire O and in section, at right angles to the View in Fig. then through the resistance wires to plate b, 1. Fig. 4 is a diagram of the connections of thence to plate b', then c, dro., to the plate e', z5 the motor field magnets and armature. supplying the brush H, which would be upon 75 A is the containing box for the rheostat, of theplate e; the current then passes to the circular shape, as shown, and is made of a sinarmature terminal N', then through the argle thin metal casting provided with ribs mature, then to the terminal N, then by the upon its under side for strengthening it. cable I to the second brush H, which would 3o Within this box are arranged rows of contacts rest upon the contact plate g; then through 8c D, D, suitably insulated and connected bythe the resistance wires to the plate la', and by resistance wires Q, Q, as shown in Fig. 4, to the copper wire O to the Vfield terminal M be more particularly described hereinafter. and then o ut over the negativev main. The C is the top of the box serving to cover its field magnets being in shunt, the insertion of 3 5 working parts and protect them from accithe'resistance reduces the effective potential 85 dental injury and dirt. on the armature, thus giving a low speed; but B is the pedal, upon which the foot of the upon shifting the position of the brushes, operator is supported, to which is secured the more and more of the resistance is cut out brush holder E serving to make the various until the brushes rest upon the contact plates 4o connections of the rheostat in ways well und', Zr, in which position the resistance is all 9o dei-stood. This pedel swings in a horizontal cut out and the effective potential is a maxiplane about a central pivot, as distinct from mum, giving a very high speed to the motor. the vertical motion of the pedals usually pro- In order to stop the motor quickly without vided; and by attaching it to a common pivot the intervention of brakes, I provide a sec-v 45 with the brush holder E, the weight of the op tion of resistance wire between the contact 9g; erator may be borne directly upon the pedal plates l, Z, upon which the brushes normally and its rotation about the center is effected stand; the result of this is that when the arwith no more fatigue than an ordinary standmature is short circuit-ed through this resisting position would give. Within the brush ance it is speedily brought to a standstill. 5o holder are secured the parts giving an elastic To provide for a little lost motion in the Ioo pedal, so that the operator may not start the motor inadvertently, idle contact plates f, f, the., are provided upon each side ot the no1'- mal position of the pedal. To run the motor in the opposite direction the motion of the pedal need only be reversed, in which case the current is passed through the armature nets being in shunt are energized in the same Way.

Having thus described my invention, what' I claim as new, and Wish to protect by Letters Patent of the United States, isy l. In a lheostat for controlling dental mo? tors, a centrally pivoted pedal adapted to i move a brush arm toward or away from a central position, and a short-circuiting resistt ance fora motor at Suchcentral position, sub

Astantialzly as described.

2. In a rheostat for controlling dental motors, a centrally pivoted pedal adapted to move the brush arm toward or away from a `central position, and idle contact plates as f,

f, upon each side of such central position; in the reversed direction, While the field'm-ag-I whereby the `arm may have a slight lost Inotion preventing the inadvertent starting of the motor.

In witness whereof I have hereunto set my hand this 7th day of July, 1893.

JONATHAN I. FISKE.

Witnesses:

JOHN W. GIBBONEY, BENJAMIN 13. HULL. 

